Got this Issue Report today when loading my server.

09.11 16:33:52 [Server] INFO [16:33:52] [Server thread/WARN] [FML]: Quark loaded a new chunk (-3, 25 Dimension: 0) during chunk population, causing cascading worldgen lag. Please report this to the mod's issue tracker. This log can be disabled in the Forge config

fml-server-latest.log

This was fixed in 1.12